This patch implements the changes required by the Vector Store authorization, as described in https://scylladb.atlassian.net/wiki/spaces/RND/pages/107085899/Vector+Store+Authentication+And+Authorization+To+ScyllaDB, that is:
- adding a new permission VECTOR_SEARCH_INDEXING, grantable only on ALL KEYSPACES
- allowing users with that permission to perform SELECT queries, but only on tables with a vector index
- increasing the number of scheduling groups by one to allow users to create a service level for a vector store user
- adjusting the tests and documentation
These changes are needed, as the vector indexes are managed by the external service, Vector Store, which needs to read the tables to create the indexes in its memory. We would like to limit the privileges of that service to a minimum to maintain the principle of least privilege, therefore a new permission, one that allows the SELECTs conditional on the existence of a vector_index on the table.
Fixes: VECTOR-201
Backport reasoning:
Backport to 2025.4 required as this can make upgrading clusters more difficult if we add it in 2026.1. As for now Scylla Cloud requires version 2025.4 to enable vector search and permission is set by orchestrator so there is no chance that someone will try to add this permission during upgrade. In 2026.1 it will be more difficult.
Closesscylladb/scylladb#25976
* github.com:scylladb/scylladb:
docs: adjust docs for VS auth changes
test: add tests for VECTOR_SEARCH_INDEXING permission
cql: allow VECTOR_SEARCH_INDEXING users to select
auth: add possibilty to check for any permission in set
auth: add a new permission VECTOR_SEARCH_INDEXING
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